de fokest



'UNI'IEB STA'IFS PA'IT FICE.

THOMAS B. DE FOREST, Ol" NIMV YORK, N. Y.

INDIA-RUBBER SPRING FOR RAILROAD-CARS, &C.

Specification of Letters Patent No. 25,100, dated August 16, 1859.

To all whom it may concern:

Be it known that I, T. B. DE FoREs'r, of New York, county of New York, in the State of New York, have invented a new and useful Improvement in the Construction of India-Rubber Springs; and I do hereby declare that the following is a full and exact description thereof, reference being had to the accompanying drawings and to the letters of reference marked lthereon.

It is a fact which observation will soon confirm that vulcanized india rubber springs are readily destroyed if any portion of the surface is exposed to friction when springing, and it is also a fact that when that material is subjected to a compressing force applied to opposite sides its spring-like property is due mainly to its spreading laterally and that if it be bound laterally the tensive force will be greatly increased. Now in the construction of my improved spring a leading objection has been to avoid friction against any solid body; and to obtain a spring which shall be very sensitive or yielding to slight loads by having it composed of small blocks free to spread all around, and which as the load increases shall come in contact with each other to give mutual lateral support, and thereby greatly increase the power of resistance to heavier loads. And to these ends my said invention consists in composing a spring of a series of blocks or sections of a ring of vulcanized india rubber, held between two parallel or nearly parallel plates and arranged with open spaces of such size between the several blocks that they shall be free to spread all around laterally to spring freely to light loads, and so that their contiguous faces shall come in contact as the load or the shocks increase and thus by mutual support acquire increasing power of resistance.

To enable others skilled in the art, to make and use my invention, I .will proceed to describe the varying modes in which I have contemplated the application of my said invention.

In the accompanying drawings, Figure l, represents a central vertical section in perspective of a spring embodying my invention. Fig. 2, represents a horizontal section at the line 0c, ac, of Fig. 1. Fig. 3, represents a longitudinal section illustrating a modified arrangement of the sections of rubber. Fig. 4, represents a vertical section of another modification of my invention and,

Fig. 5, represents a horizontal section at the line y, y, of Fig. 4.

In Figs. 1, 2 and 3, A, represent the sectional blocks of vulcanized india rubber, two sets or series of which are illustrated as being employed separated from each other by a metallic plate, a, and confined vertically by the bottom plate, B, and the top plate, c, of the case, C, which plate, B, and case top, c, are held in contact with the sectional blocks of rubbers by means of a bolt, Y), passing through said plate, case top, c, and the center plate, a, and furnished at its lower end with a washer head, d, and at its upper extremity with a nut, c.

The case, O, is formed with an annular flange, f, which projects up even with, that is, in the same plane, with the tops of bolt, Y), and nut, c, and on which, together with the end of said bolt, rests the weight to be Supported. The diameter of the plate, a, is a little less than the internal diameter of the case, C, as is also the diameter of the bottom plate, B, in order that the said case, C, may freely move up and down, outside the said plate. A

D, is an auxiliary block of rubber which may sometimes be advantageously employed and consists of a small annular ring as represented, fastened onto the lower surface of the bolt head, d, in such manner that when the said bolt head descends (with the case, O,) the said rubber, D, will come in contact with the surface Von which the lower plate, B, rests and form a spring or cushion.

The section or blocks, A, of rubber are so formed and arranged relatively vto each other that the ends, A2, (see Figs. 2 and 5) which are nearest the center cannot come in Contact with each other or with the center bolt (when one is used) and the outer surfaces, A3, (see Fig. 2) are so far from the case, O, (when one is used) that they cannot come in contact with it; but the adjacent sides, A4, of the sections or blocks are at such distance from each other, that when they are considerably compressed, their adjacent sides, A4 shall come into contact and support each other, then act as a continuous ring or annulus as illustrated by the red lines in Fig. 2, so that the further yielding to any increasing force shall be limited to the inner and outer surfaces of a ring or annulus as illustrated by the blue lines in Fig. 2: by thus arranging the sections, A, of rubber, a more desirable result is produced, than would be, by the arrangement of said sections closely together (which would render the operation similar to that of an annular) because when 4the weight is slight and the consequent power acting on the spring moderate the series of blocks of rubber being free to spread each one in four directions will be much more sensitive or yielding than if they were laterally sustained or were aggregated into a continuous ring or annulus capable of yielding or spreading only in two directions. At Fig. 3, is illustrated the action of the blocks of rubber, A, with a smallar number of sections and it is obvious that the number, size and form of the sections of rubber may be varied without departing from the principle or character of my invention.

The modification of my improvement as illustrated at Figs. 4 and 5 consists in the employment, in lieu of metallic case, C, of bands, 0, of rubber cloth, or other elastic material fitting closely between the pairs of metallic plates, and encircling tightly 'the series of sections, A, and in using simply the metallic plates, m, onto which the sections, A, are secured (by cementing or otherwise) without any securing bolt or auxiliary spring cushion: This modification of my improvement may sometimes be more economical and advantageous than the mode of construction first described as it supersedes the necessity of using the metallic case, C, and bolt, b, with the appendages thereby rendering the spring less costly, equally efficient in operation and more readily transported.

I am aware that attempts have been made to render available old pieces of vulcanized india rubber or broken springs in the manufacture of new springs by placing in a cup or other vessel a quantity of pieces or particles of vulcanized india rubber, mixed with other material, to prevent the solidification of the rubber and compressed within confining vessel by a plunger' or plate, but such method of forming a spring of india rubber, I do not consider in any manner analogous to my invention, or as possessing any practical utility as the pieces of rubber so applied are necessarily subjected to constant friction; and it is a well-known fact, that the most important consideration in the employment of india rubber in the formation of springs is, to apply it under such circumstances that while itselastic property may be rendered available, it shall be subjected to the least possible amount of friction.

I am also aware that in the construction of springs, sections of rubber have been employed, confined between annular rings or flanges and compressed by other annular flanges entering between the flanges which confined the sections, but I do not consider such an arrangement as at all conflicting with my improvement as the sections of rubber thus employed are subjected to constant friction against the confining flanges or rings, and their utility as springs thus destroyed.

I do not desire to have it understood that my improvement is in any manner similar to the springs thus referred to, nor to make claim to any such, neither do I wish to limit my claim of invention to any exact number or shape of sections of rubber employed, as either may evidently be varied without delparting from the character of my invention:

That I claim as my invention and desire to secure by Letters Patent is Composing a spring of a series of blocks, or segments of a circle, of vulcanized india rubber placed and held between two parallel plates or equivalents substantially as described, but this I only claim when the series of blocks are so arranged and held between the two parallel plates that their contiguous faces shall not come in contact under light loads, but shall come into contact and give mutual support as the load increases, substantially as and for the purpose specified. In testimony whereof I have hereunto set my hand and seal this first day of April, 1859.

THOMAS B. DE FOREST. [1.. s] Witnesses:

J. N. MGINTIRE, HENRY W. TURPIN. 

